CVE-2023-39829
📋 TL;DR
This vulnerability is a stack overflow in Tenda A18 routers that allows remote attackers to execute arbitrary code by sending a specially crafted request to the fromSetWirelessRepeat function. It affects users running Tenda A18 routers with firmware version V15.13.07.09. Attackers can potentially take full control of affected devices.
💻 Affected Systems
- Tenda A18 Wireless Router
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete device compromise, allowing attackers to intercept network traffic, install malware, or pivot to internal networks.
Likely Case
Router compromise enabling network traffic monitoring, DNS hijacking, or botnet recruitment.
If Mitigated
Limited impact if device is behind firewall with restricted WAN access and regular patching.
🎯 Exploit Status
Public proof-of-concept available on GitHub. Exploitation requires sending crafted HTTP request to vulnerable endpoint.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Tenda website for latest firmware
Vendor Advisory: Not publicly available
Restart Required: Yes
Instructions:
1. Visit Tenda support website. 2. Download latest firmware for A18 model. 3. Access router admin interface. 4. Navigate to firmware upgrade section. 5. Upload and install new firmware. 6. Reboot router.
🔧 Temporary Workarounds
Disable Wireless Repeater Function
allDisable the vulnerable wireless repeater functionality if not needed
Access router admin interface > Wireless Settings > Disable WDS/Repeater mode
Restrict WAN Access
allConfigure firewall to block external access to router admin interface
Configure firewall to block port 80/443 from WAN to router IP
🧯 If You Can't Patch
- Isolate router on separate VLAN with strict network segmentation
- Implement intrusion detection monitoring for exploit attempts
🔍 How to Verify
Check if Vulnerable:
Check firmware version in router admin interface under System Status or About pageCheck Version:
curl -s http://router-ip/status.asp | grep firmwareVerify Fix Applied:
Verify firmware version is updated to newer than V15.13.07.09📡 Detection & Monitoring
Log Indicators:
- Unusual HTTP POST requests to fromSetWirelessRepeat endpoint
- Large payloads sent to router web interface
Network Indicators:
- Exploit traffic patterns matching public PoC
- Unexpected connections to router admin interface from external IPs
SIEM Query:
source="router_logs" AND (uri="*fromSetWirelessRepeat*" OR data_size>1000)